Modular knee prosthesis

ABSTRACT

A modular prosthetic knee system used to replace the natural knee. The system includes a femoral knee prosthesis and a tibial knee prosthesis. Both prostheses are formed of modular components that are connectable in-vivo to form the prosthetic knee system. The femoral knee prosthesis includes two separate components, a lateral condyle and medial condyle; and the tibial knee prosthesis includes a multiple separate components, a medial baseplate, a lateral baseplate, a medial insert, and a lateral insert. The medial and lateral baseplate are connectable to form a complete baseplate with the medial and lateral inserts connectable to the complete baseplate.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. Ser. No.10/302,066 filed on Nov. 22, 2002.

FIELD OF THE INVENTION

[0002] The present invention relates to a modular knee prosthetic systemused to replace the natural knee and, more particularly, to aunicompartmental and bicompartmental modular knee system having variousdistal posterior femoral components that are interchangeable with eachother and with various patellar-femoral joint components.

BACKGROUND OF THE INVENTION

[0003] In knee artlroplasty, portions of the natural knee joint arereplaced with prosthetic knee components. Typically, these componentsinclude a tibial component, a femoral component, and a patellarcomponent. The femoral component generally includes a pair of spacedcondyles that articulate with the tibial component. The components aremade of materials that exhibit a low coefficient of friction when theyarticulate against one another.

[0004] When the articulating ends of both the femur and tibia arereplaced, the procedure is referred to as total knee replacement or TKR.Much effort has been devoted to performing a TKR that restores normal,pain-free, functions of the knee in a short period of postoperativetime.

[0005] Several factors lead to long-term success of TKR. One importantfactor is soft-tissue balancing. The normal, non-diseased knee isconsidered properly balanced when the deflection between the medial andlateral condyles and the tibial plateau is equal throughout the entirerange of motion. If this balance is not achieved, abnormal kneekinematics occurs, and the TKR components and surrounding soft tissuecan experience excessive forces even during normal range of motion.These excessive forces can further cause an abnormal gait, pain, andearly failure of total knee replacements.

[0006] Soft-tissue balancing can be achieved in TKR if the componentsare correctly sized and properly placed. In order to achieve properplacement during a TKR surgery, equal tibial-femoral flexion gaps andextension gaps must be achieved. The flexion gap is defined as the spacebetween the posterior coronal cut on the distal femur and transverse cuton the proximal tibia, while the knee is in 90° of flexion. Theextension gap is defined as the space between the transverse cut ondistal femur and the transverse proximal tibial cut while the knee is incomplete extension. Soft tissue balance occurs when stability isachieved in both flexion and extension.

[0007] During a TKR surgery, a series of surgical compromises is oftenused to achieve a balance of flexion and extension gaps. Elevation ofthe joint line is one such compromise. An elevation of the joint lineoccurs when there is a change in distance from the original articularsurface to the newly reconstructed surface. This change in distance istypically measured as a vertical distance from a fixed point on thetibia.

[0008] For several reasons, the joint line can become elevated.Excessive medial or lateral releases and insertion of thicker plasticinserts can cause the line to elevate. Further, the joint line canbecome elevated when the femoral component is undersized. Such anundersize can create a larger flexion gap than extension gap. To balancethese gaps, more bone may need to be removed from the distal femur; andthis additional bone loss raises the joint line.

[0009] Unfortunately, a change in the joint line can negatively affect awide array of components and operations of the knee, such as thefunctions of the PCL, collateral ligaments, and patello-femoral jointmechanics. These problems can be avoided or minimized if elevation ofthe joint line is reduced or, better yet, eliminated.

[0010] Another surgical compromise often occurs when soft tissue gapsare not balance when implanting a distal femoral knee prosthesis. Ahealthy balance of these gaps maintains the natural kinematics of thepatient. The compromise occurs when the operating surgeon must chooseone of six or seven differently sized distal femur prostheses; and thesize of these prostheses may not exactly match the size of an idealprosthesis for the patient. For example, current anterior referencingmethodology to achieve balanced flexion and extension gaps in mostpatients requires the surgeon to slightly alter the joint line. If ananterior referencing sizing guide falls between two sizes, the surgeoncould be forced to choose a smaller size prosthesis so the flexion gapis not overstuffed. A smaller prosthesis, in such an instance however,can consequently enlarge the flexion gap as much as 3.5 mm to 4 mm.

[0011] Another important factor that contributes to the long-termsuccess of total knee replacements is loading and kinematics of thepatellar-femoral joint. Complications associated with patella failuresaccount for up to 50% of TKR revision procedures. Many of thesecomplications occur because of improper or unnatural loading orkinematics of the patellar-femoral joint. For example, overstuffing thepatellar-femoral joint is one major cause of improper soft tissueloading and kinematics. In this regard, many surgeons use posteriorreferencing instrumentation when sizing and preparing the femur forimplant resurfacing. On the one hand, posterior referencing allows thesurgeon to balance the tibial-femoral flexion and extension gaps withoutnecessarily changing the joint line. On the other hand though, the useof posterior referencing increases the risk of notching the anteriorcortex and overstuffing the patellar-femoral joint.

[0012] In short, current knee systems often require an unwanted surgicalcompromise. Such compromises can alter the natural joint line of thepatient or overstuff the patellar-femoral joint. Unfortunately, thesecompromises also negatively affect the natural kinematics of the patientand can, for example, increase strain on the PCL and other tendons andligaments, increase implant wear, and decrease implant function.Patients may be more likely to experience pain, reduced function, andmore frequent revision surgeries.

[0013] Current knee systems have other disadvantages as well. Distalfemoral prostheses are simply too large to fit through small incisionsthat are used during a minimally invasive surgery or MIS. MIS has manyadvantages over traditional surgical techniques since it providesshorter incisions, faster recovery times, and generally less pain forthe patient. The surgical technique, though, has limitations. As noted,current tricompartmental distal femoral prostheses cannot fit throughthe small incision, usually three inches in length. To date, MIS hasbeen generally limited to unicondylar or unicompartmental kneereplacement prostheses that are much smaller in size and able to fitthrough the incision.

[0014] It would be advantageous to have a modular knee prosthetic systemthat has advantages over prior knee prosthetic systems and techniques.Such a system would have greater modular versatility to accommodatedifferent patient anatomies and joint conditions while maintaining arelatively low component count.

SUMMARY OF THE INVENTION

[0015] The present invention is directed toward a modular knee systemhaving various distal posterior femoral components that areinterchangeable with each other and with various patellar-femoral jointcomponents. Preferably, the modular knee system has a variety ofcomponents that are interchangeable and connectable to resurface thedistal femur using either a unicompartmental femoral knee prosthesis ora bicompartmental femoral knee prosthesis. These components include amedial distal posterior femoral component, a lateral distal posteriorfemoral component, a patellar-femoral joint component, and aninterconnection mechanism to modularly connect the components together.

[0016] The knee system of the present invention allows for modularitybetween the distal posterior femoral components and the patellar-femoraljoint components. The interchangeability of these components enablesmixing and matching of multiple sizes and thicknesses of all components.This interchangeability allows the surgeon to resurface the distal femurwithout overstuffing the patellar compartment or changing the naturaltibial-femoral joint line.

[0017] One advantage of the present invention is that the modularity ofcomponents gives the surgeon more diversification when choosing sizesfor the medial and lateral condyles. The deflection between thesecondyles and the tibial plateau, thus, can be more easily equalizedthroughout the range of motion. As such, the soft-tissue can be moreeasily balanced.

[0018] Another important advantage of the present invention is that thevarious knee components are interchangeable and can be more correctlysized for an accurate fit. As such, more equal tibial-femoral flexiongaps and extension gaps can be achieved. In particular, excessive medialor lateral releases and insertion of thicker plastic inserts can be moreeasily avoided. Elevation of the joint line in these situations can beminimized or, better yet, avoided.

[0019] Further, modularity of the knee components enables a more naturalbalance between soft tissue gaps when implanting a distal femoral kneeprosthesis. If, for example, different sizing occurs between the medialand lateral sides of the distal posterior components, differently sizeddistal posterior femoral components can be connected together toaccommodate this variance of sizing. Thus, differently sized condylesmay be implanted on the medial and lateral sides to more closelyreplicate the natural anatomy of the patient. Further, additional bonemay be saved and not unnecessarily removed from the distal femur or fromthe tibia.

[0020] Since the present invention can more readily accommodate varioussizes during knee replacement surgery, the natural location of the jointline can be maintained. Certain problems associated with altering thejoint line can be avoided or minimized.

[0021] The present modular knee system can also help achieve naturalloading and kinematics of the patellar-femoral joint. For example, thevarious sizes and interchangeability of knee components can enable morecorrectly sized patellar-femoral joints. In some situations,overstuffing can be avoided.

[0022] As another important advantage, all of the individual componentsof the modular knee system of the present invention is small enough tobe used during minimally invasive surgery or MIS. Each modular componentcan fit through a three inch incision. Even more importantly, themodular components can be assembled after being inserted through theincision. Thus, the modular knee system can be used with eitherunicompartmental, bicompartmental, or tricompartmental procedures (i.e.,either unicondylar, bicondylar, or tricompartmental knee replacements).

[0023] As yet even another advantage, the modularity of the present kneesystem reduces the overall number of individual components required in aknee product line. This reduction has significant cost savings.

[0024] Accordingly, the present invention comprises a combination offeatures and advantages that overcome various problems, deficiencies, orshortcomings associated with prior devices. The various features andadvantages of the invention will be readily apparent to those skilled inthe art upon referring to the accompanying drawings and reading thefollowing detailed description of the preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a more detailed description of preferred embodiments of thepresent invention, reference will now be made to the accompanyingdrawings, wherein:

[0026]FIG. 1 illustrates a perspective view of two medial distalposterior femoral components of the present invention.

[0027]FIG. 2 illustrates a side view of the femoral components of FIG.1.

[0028]FIG. 3 illustrates a perspective view a patellar-femoral jointcomponent of the present invention.

[0029]FIG. 4 illustrates the condylar surface of the patellar-femoraljoint component of FIG. 3.

[0030]FIG. 5 illustrates an exploded view of the two medial distalposterior femoral components of FIG. 1 connecting to thepatellar-femoral joint component of FIG. 3.

[0031]FIG. 6 illustrates a perspective view of a bicompartmental femoralknee with the two medial distal posterior femoral components of FIG. 1connected to the patellar-femoral joint component of FIG. 3.

[0032]FIG. 7 illustrates a single medial distal posterior femoralcomponent.

[0033]FIG. 8 illustrates an exploded view of a unicompartmental femoralknee with the single medial distal posterior femoral component of FIG. 7and a single patellar-femoral joint component.

[0034]FIG. 9 illustrates a unicompartmental femoral knee with the medialdistal posterior femoral component and the patellar-femoral jointcomponent of FIG. 8 connected together.

[0035]FIG. 10 illustrates an exploded view of a first modular connectionof a single medial distal posterior femoral component connecting to apatellar-femoral component with dual condylar surfaces.

[0036]FIG. 11 illustrates a perspective view of the components of FIG.10 connected together.

[0037]FIG. 12 illustrates an exploded view of a second modularconnection of a single medial distal posterior femoral componentconnecting to a patellar-femoral component with dual condylar surfaces.

[0038]FIG. 13 illustrates a perspective view of the components of FIG.11 connected together.

[0039]FIG. 14 illustrates a perspective view of a unicompartmentalfemoral knee with the medial distal posterior femoral component and thepatellar-femoral joint component connected to a tibial insert and tibialbaseplate.

[0040]FIG. 15 illustrates a first exploded view of a five-piece femoralknee.

[0041]FIG. 16 illustrates a second exploded view of the five-piecefemoral knee of FIG. 15.

[0042]FIG. 17 illustrates a perspective view of the five-piece femoralknee of FIG. 15 wherein the five components are connected together toform a biocompartmental femoral knee.

[0043]FIG. 18A illustrates a perspective view of a two-piecebicompartmental femoral knee prosthesis.

[0044]FIG. 18B illustrates a perspective view of the two-piecebicompartmental femoral knee prosthesis of FIG. 18A.

[0045]FIG. 18C illustrates another perspective view of the two-piecebicompartmental femoral knee prosthesis of FIG. 18A.

[0046]FIG. 18D illustrates a perspective view of the femoral kneeprosthesis of FIG. 18A connected together.

[0047]FIG. 19A illustrates a perspective view of another embodiment of atwo-piece bicompartmental femoral knee prosthesis.

[0048]FIG. 19B illustrates another perspective view of the two-piecebicompartmental femoral knee prosthesis of FIG. 19A.

[0049]FIG. 20A illustrates a perspective view of a complete kneeprosthesis including a femoral knee prosthesis and a tibial kneeprosthesis.

[0050]FIG. 20B illustrates a side view of the knee prosthesis of FIG.20A.

[0051]FIG. 20C illustrates another perspective view of the kneeprosthesis of FIG. 20A.

[0052]FIG. 20D illustrates another perspective view of the kneeprosthesis of FIG. 20A.

[0053]FIG. 20E illustrates a perspective view of the assembled tibialinsert.

[0054]FIG. 21A illustrates a perspective view of another embodiment of acomplete knee prosthesis including a femoral knee prosthesis and atibial knee prosthesis.

[0055]FIG. 21B illustrates another perspective view of the kneeprosthesis of FIG. 21A.

DETAILED DESCRIPTION

[0056]FIGS. 1 and 2 illustrate two separate distal posterior femoralcomponents generally at 10. One component is a medial distal posteriorfemoral component (DPFC) 12, and a second component is a lateral DPFC14. Both femoral components 12 and 14 have a smooth outer condylarsurface 16 adapted to articulate with a tibial insert. Surface 16 isshaped as a partial femoral condyle that extends from a proximal portion18 to a distal portion 20. A bone engaging surface 22 is oppositelydisposed from the condylar surface 16. This surface 22 includes severalflat, planar sections 24 that extend from the proximal portion 18 to thedistal portion 20. A stem 26 projects upwardly from the bone engagingsurface 22. This stem 26 has a tapering cylindrical shape and is adaptedto be inserted in the intramedullary canal of a femur.

[0057] The medial and lateral DPFC also includes a connector 28 locatedon an end surface 30 of the proximal portion 18. The connectors 28 areshaped as cylindrical, tapering recesses. These recesses extend into thebody of the femoral components.

[0058]FIGS. 3 and 4 illustrate a patellar-femoral joint component (PFJC)40. The PFJC 40 has a smooth outer condylar surface 42 adapted toarticulate with a tibial insert. Surface 42 is shaped as a partialfemoral condyle that extends from a proximal portion 44 to a distalportion 46. A bone engaging surface 48 is oppositely disposed from thecondylar surface 42. This surface 48 includes several flat, planarsections 50 that extend from the proximal portion 44 to the distalportion 46.

[0059] The PFJC 40 also includes a connection mechanism 54 located on anend surface 56 of the proximal portion 44. The connection mechanism 54is shaped as two separate, spaced projections having a cylindrical,tapering body. The projection extends outwardly from the body of thePFJC.

[0060] Turning also to FIGS. 5 and 6, connection mechanism 54 of thePFJC 40 is adapted to engage and connect with the connectors 28 on boththe medial DPFC 12 and lateral DPFC 14. Specifically, the projections ofthe connection mechanism 54 slideably press-fit to lock into therecesses of the connectors 28. This connection may Utilize a Morse taperfit.

[0061] One skilled in the art will appreciate that many different meansexist for connecting the distal posterior femoral components 10 to thePFJC 40. In this regard, the connectors 28 could be configured astapering male projections while the connection mechanism is configuredas a tapering recess adapted to receive the projections. Otherconnections exist as well. For example, the connection mechanism couldbe configured to snapingly engage the connectors or configured as abayonet type connection. Further, the connection between the connectionmechanism 54 and the connectors 28 could be permanent or removeablyconnected.

[0062] It is important to note that when the medial DPFC 12 and thelateral DPFC 14 connect to the PFJC 40, these components form acomplete, full femoral knee prosthesis 60 (see FIG. 6). This prosthesis60 functions as a traditional one-piece bicompartmental femoralprosthesis. As such, the prosthesis 60 may be used as a bicompartmentalfemoral prosthesis for total knee replacements. The important advantageof the present invention, though, is that the prosthesis 60 is composedof several modular pieces. Specifically, the prosthesis is composed ofthree separate, interconnectable pieces, namely a medial DPFC 12, alateral DPFC 14, and a PFJC 40.

[0063] As noted, the distal posterior femoral components have a partialcondylar surface 16, and the PFJC 40 has a partial condylar surface 42.When these components are connected together to form the femoral kneeprosthesis 60, then the surfaces 16 and 42 join and form a full condylarsurface 62. This surface 62 extends from the distal portion 20 of thedistal posterior femoral components to the distal portion 46 of thePFJC. Preferably, this surface 62 is continuous and seamless at thejunction or union 66 from surface 16 to surface 42. No bumps, ridges,seams, indentations, channels, or the like should exist at the junction66 where the surfaces meet.

[0064] FIGS. 7-9 illustrate one of the modular properties of the presentinvention. FIG. 7 shows a single distal posterior femoral component 80.DPFC 80 is similarly configured to the distal posterior femoralcomponents shown in FIGS. 1 and 2. This component 80 may be shaped foruse as a medial DPFC, lateral DPFC, or generic and useable for bothmedial and lateral indications.

[0065]FIG. 8 shows a patellar-femoral joint component 90 that issimilarly configured to the PFJC 40 shown in FIGS. 3 and 4. Oneimportant exception is the PFJC 90 is not shaped for bicompartmental usebut for unicompartmental use. More specifically, the PFJC 90 has asingle smooth outer condylar surface 92 adapted to articulate with atibial insert. Surface 92 is shaped as a partial single femoral condylethat extends from a proximal portion 94 to a distal portion 96. A boneengaging surface 98 is oppositely disposed from the condylar surface 92.This surface 98 includes several flat, planar sections 100 that extendfrom the proximal portion 94 to the distal portion 96. The PFJC 90 alsoincludes a connection mechanism 102 located on an end surface 104 of theproximal portion 94. The connection mechanism 102 is shaped as a singleprojection having a cylindrical, tapering body. This projection extendsoutwardly from the body of the PFJC and is adapted to fit into aconnector 106 shaped as a recess on the DPFC 80. The connection betweenthe DPFC 80 and PFJC 90 are similar to the connections discussed inconnection with FIGS. 1-6; one difference is the connection in FIGS. 7-9uses a single connection mechanism or projection and a single connectoror recess.

[0066] As shown in FIGS. 7-9 then, one advantage of the presentinvention that the DPFC 80 and the PFJC 90 connect together to form acomplete femoral knee prosthesis 110 (see FIG. 9). This prosthesis 110functions as a traditional one-piece unicompartmental femoralprosthesis. One important advantage of the present invention is that theunicompartmental prosthesis 110 is composed of several modular pieces.Specifically, the prosthesis is composed of two separate,interconnectable pieces, namely a DPFC 80 and a PFJC 90.

[0067] FIGS. 10-13 show more examples of the diversification ofmodularity of the present invention. These figures show a DPFC 120 thatis connectable to a PFJC 122. The DPFC 120 is similar to the distalposterior femoral components shown in FIGS. 1 and 2, and PFJC 122 issimilar to the patellar-femoral joint component shown in FIGS. 3 and 4.In FIGS. 10 and 11 though, the PFJC 122 connects to a single DPFC 120 onthe medial side. By contrast, in FIGS. 12 and 13, the PFJC 122 connectsto a single DPFC 120 on the lateral side.

[0068]FIG. 14 shows one example how the modular components of thepresent invention can be utilized. Here, a DPFC 130 and a PFJC 132 areconnected together to form a unicompartmental femoral prosthesis 134.This prosthesis 134 has an extended or enlarged stem 136, but otherwiseis generally similar to the unicompartmental prosthesis 110 shown inFIG. 9.

[0069] As shown in FIG. 14, the unicompartmental femoral prosthesis 134has a bone engaging surface 140 with a porous or Cancellous-StructuredTitanium (CSTi) coating to enhance bone engagement. An outerarticulating condylar surface 142 abuts against a tibial insert 144.This insert 144 is connected to a tibial baseplate 146 having a baseportion 148 and threaded screw or stem 150 extending downwardly from thebase portion. The tibial insert 144 and baseplate 146 are known to thoseskilled in the art and may be similar, for example, to those sold byCenterpulse Orthopedics Inc. of Austin, Tex.

[0070] FIGS. 15-17 show yet more examples of the diversification ofmodularity of the present invention. Here, a complete femoral kneeprosthesis 160 is shown. This prosthesis 160 includes a single PFJC 162and two DPFC 164 and functions as a traditional bicompartmentalprosthesis as shown and described in FIG. 6. As one importantdifference, each DPFC 164 is formed from two separate components, namelya top half 166 and a bottom half 168. When the top half 166 and bottomhalf 168 are connected, they function as the DPFC described in FIGS. 1and 2. Here though, each top half 166 includes a connector 170; and eachbottom half includes a connector 172. The connectors 170 and 172 areshown as recesses and projections, respectively, and slideably press-fittogether to form single distal posterior femoral components.

[0071] As discussed in connection with connection mechanism 54 of PFJC40 and connectors 28 of DPFC 12 and 14 in FIGS. 5 and 6, the connectors170 and 172 may have various configurations known to those skilled inthe art to achieve a permanent or removable connection between the tophalf 166 and bottom half 168. Each articulating component may attach toa third body connection piece that would bridge the components.

[0072] One important advantage of the present invention is that all ofthe individual, separate distal posterior femoral components and thepatellar-femoral joint components are adapted to be used in minimallyinvasive surgery (MIS) techniques. MIS is intended to allow for themaximum preservation of bone stock, restoration of kinematics, minimaldisturbance of the patellar tendon, and rapid rehabilitationpostoperatively. During an MIS knee surgery, a ½ to 3 inch incision ismade. The DPFC and PFJC are small enough to fit through this incision.Thus, these components can be fit through the incision and thenassembled to form a unicompartmental femoral knee, bicompartmentalfemoral knee, or hybrid of these two (the various embodiments beingshown in FIGS. 1-17 ).

[0073] Another advantage of the present invention is the distalposterior femoral components can be made to be completelyinterchangeable. Thus, no need exists for separate medial/lateral orleft/right components. Further the DPFC and PFJC can be made to havevarious sizes and thicknesses to accommodate various patient needs. Thecomponents can even be coated with CSTi or other coatings known to thoseskilled in the art to enhance bone growth or cement retention.

[0074] As another advantage, the total modular design of the presentinvention, in addition to being compatible with MIS, allows the surgeonto resurface only the anatomy that requires resurfacing. Thus, thesurgeon can assemble a femoral knee prosthesis to better fit the needsof the individual patient and minimize or eliminate unnecessary bonecuts.

[0075] Further yet, modularity of the present invention can also savethe manufacturer tremendous inventory costs, especially if existinginstrumentation can be used. The charts below summarize one potentialmanufacturing cost savings. The chart on the left shows a typical numberof components for a non-modular femoral knee system. The chart on theright shows a typical number of components utilizing the modularcomponents of the present invention. As shown, an inventory can bereduced by approximately 41 components.

[0076] More advantages of the present invention are listed below and areexplained in the Summary section:

[0077] Full modularity between anterior and distal and posterior femoralcomponents eliminates the need for the surgeon to compromise thepatient's natural gait. The system provides the surgeon with flexibilityand control in implant sizing.

[0078] Multiple distal and posterior components allow multiple ethnicanatomies to be replicated with one knee system. For instance, Asianpatients may require longer posterior condyles to replicate theirnatural anatomy. The option of attaching an Asian unicondylar componentto a PFJC will allow the surgeon to convert the prosthesis to allow forhigh flexion.

[0079] A stand-alone patella-femoral component would allow the PFJC tobe included in the same system as the primary knee.

[0080] A stand-alone distal/posterior component can be used as an MISunicompartmental prosthesis. Thus the surgeon can make theintraoperative choice of unicompartmental or bicompartmental procedure.

[0081] A stand-alone Asian distal/posterior component would allow aunicompartmental or bicompartmental procedure that would closelyreplicate the Asian anatomy.

[0082] Posterior femoral components of two different thickness optionsmay be implanted on the medial and lateral condyles. This option willallow the surgeon to correctly replicate the natural patient anatomy.

[0083] An attachment or connection feature and mechanism between theanterior PFJC and the distal components. The attachment allows a surgeonto convert a unicompartmental knee to a primary knee by simply attachingthe anterior component to the existing distal/posterior component(s).The attachment features would also allow the surgeon to convert a PFJCto a total knee replacement without revising the PFJC.

[0084] FIGS. 18A-18C show another embodiment of the invention. Abicompartmental femoral knee prosthesis 200 comprises two separate andmodular components, a lateral femoral knee condyle 202 and a medialfemoral knee condyle 204. Both femoral components 202 and 204 have asmooth outer condylar surface 206A and 206B, respectively, adapted toarticulate with a tibial insert. Each surface 206 is shaped as a curvedfemoral condyle that extends from a proximal portion 208 to a distalportion 210. A bone engaging surface 212 is oppositely disposed from thecondylar surface 206. This surface 212 includes several flat, planarsections 214 that extend from the proximal portion 208 to the distalportion 210. An optional stem (such as stem 26 shown FIG. 1) can beformed to each condyle for insertion in the intramedullary canal of afemur.

[0085] The medial and lateral condyles also include a connection orlocking mechanism 218 located on a side surface 220A and 220B,respectively. This locking mechanism includes a male component 222 and afemale component 224. The male component is shaped as a rectangularprotrusion that extends outwardly from side surface 220A. The femalecomponent is shaped as a rectangular recess that extends into sidesurface 220B. These components are shaped to lockingly engage in a Morsetaper connection.

[0086] Looking to FIG. 18D, when the medial and lateral femoral kneecondyles connect together, these two components form a complete, fullfemoral knee prosthesis 230. This prosthesis functions as a traditionalone-piece bicompartmental femoral prosthesis and includes a full outercondylar surface 232 adapted to articulate with a tibial insert andnatural patella or patellar prosthesis. The prosthesis may be used as abicompartmental femoral prosthesis for total knee replacements.

[0087] Looking to FIGS. 18C and 18D, preferably the prosthesis isdivided across a sagital plane or medial-lateral plane 234 (shown inFIG. 18C). This plane splits the prosthesis into two separate anddistinct halves, the lateral condyle 202 and medial condyle 204. Oncecondyles 202 and 204 are connected, surface 232 is continuous. As shownin FIG. 18D, this surface 232 is preferably seamless at the junction orunion where condyle 202 connects to condyle 204. No bumps, ridges,seams, indentations, channels, or the like should exist at the junctionwhere surfaces 206A and 206B meet.

[0088]FIGS. 19A and 19B show another embodiment of the invention. Abicompartmental femoral knee prosthesis 300 comprises two separate andmodular components, a lateral femoral knee condyle 302 and a medialfemoral knee condyle 304. Both femoral components 302 and 304 have asmooth outer condylar surface 306A and 306B, respectively, adapted toarticulate with a tibial insert. Each surface 306 is shaped as a curvedfemoral condyle that extends from a proximal portion 308 to a distalportion 310. A bone engaging surface 312 is oppositely disposed from thecondylar surface 306. This surface 312 includes several flat, planarsections 314 that extend from the proximal portion 308 to the distalportion 310. An optional stem (such as stem 26 shown FIG. 1) can beformed to each condyle for insertion in the intramedullary canal of afemur.

[0089] The medial and lateral condyles also include a connection orlocking mechanism 318 located on a side surface 320A and 320B,respectively. This locking mechanism includes a male component 322 and afemale component 324. The male component is shaped as a rectangularprotrusion that extends outwardly from side surface 320A. The femalecomponent is shaped as a rectangular recess that extends into sidesurface 320B. These components are shaped to lockingly engage in a Morsetaper connection.

[0090] When the medial and lateral femoral knee condyles of FIGS. 19Aand 19B connect together, these two components form a complete, fullfemoral knee prosthesis (identical to the prosthesis 230 shown in FIG.18D). This prosthesis functions as a traditional one-piecebicompartmental femoral prosthesis and includes a full outer condylarsurface adapted to articulate with a tibial insert and natural patellaor patellar prosthesis. The prosthesis may be used as a bicompartmentalfemoral prosthesis for total knee replacements.

[0091] As shown in FIG. 19B, the prosthesis 300 is divided across twodifferent planes, medial-lateral plane 334 and an anterior-posteriorplane 336. These planes split the prosthesis into two separate anddistinct halves, the lateral condyle 302 and medial condyle 304.Further, the planes do not equally split the prosthesis; two condyleshave different shapes. The lateral condyle 302 has an enlargedpatellar-femoral joint section 340 that forms a portion of theprosthetic trochlear groove adapted to articulate with a natural orprosthetic patella Section 340 has a somewhat rectangular shape thatextends beyond the medial-lateral plane 334 and above theanterior-posterior plane 336.

[0092] Once condyles 302 and 304 are connected, preferably they form acontinuous and seamless junction or union where the condyles connect. Nobumps, ridges, seams, indentations, channels, or the like should existat the junction where surfaces 306A and 306B meet.

[0093] One skilled in the art will appreciate that many different meansexist for connecting the lateral and medial femoral knee condyles ofFIGS. 18 and 19. In this regard, the locking mechanism 218 (FIGS.18A-18C) and 318 (FIGS. 19A and 19B) could be configured as other typesof tapered locking or press-fit connections. The male and femalecomponents could be shaped as cylindrical projections and recesses,respectively. Further, the locking mechanism could be configured to usea bayonet type connection or configured to snappingly engage each other.Further, the connection between these two condyles can be permanent orremoveable. Further yet, multiple locking mechanism can be employed.These mechanisms can be positioned along the side surface or elsewhereon the femoral condyles.

[0094] FIGS. 20A-20D illustrate a prosthetic knee system or a completeknee prosthesis 400 adapted to be used for total knee arthroplasty.System 400 includes two main components, a femoral knee prosthesis 402and a tibial knee prosthesis 404. The femoral knee prosthesis 402comprises two separate and modular components, a lateral femoral kneecondyle 406 and a medial femoral knee condyle 408. These components areidentical to the condyles 202 and 204 discussed in connection with FIGS.18A-18D, and reference should be made to those figures for a descriptionof condyles 406 and 408.

[0095] The tibial knee prosthesis 404 includes two separate and modularcomponents, a tibial insert 420 and a tibial baseplate 422. The tibialbaseplate 422 generally has an elliptical or oval shape and comprises alateral component 430 and a medial component 432. These two componentsgenerally have a half-moon shape with rounded ends 436 and planarsurfaces 438 and 440. Surface 438 is oppositely disposed from surface440 and is adapted to engage a planar bone surface of the natural tibia.Surface 440 is adapted to engage and connect to the tibial insert 420and includes a wall or shoulder 441 that extends around the outerperimeter. Cylindrical bores 443 extend through the tibial baseplate andare adapted to receive bone screws for fastening the baseplate to tibialbone.

[0096] The medial and lateral components also include a connection orlocking mechanism 442 located on side surfaces 444A and 444B. Thislocking mechanism includes a male component 446 and a female component448. The male component is shaped as a rectangular protrusion thatextends outwardly from side surface 444B. The female component is shapedas a rectangular recess that extends into side surface 444A. Thesecomponents are shaped to lockingly engage in a Morse taper connection toconnect the components together.

[0097] When the lateral component 430 and medial component 432 connecttogether, these two components form a complete and assembled tibialbaseplate. In this assembled state, the tibial baseplate functions as atraditional one-piece, integrally formed tibial baseplate. The assembledbaseplate may be used as a bicompartmental tibial baseplate for totalknee replacements.

[0098] The tibial insert 420 generally has an elliptical or oval shapeand comprises a lateral component 450 and a medial component 452. Thesetwo components generally have a half-moon shape with rounded ends 456and are complementary to the shapes of the lateral component 430 andmedial component 432, respectively. Both components 450 and 452 have asmooth outer condylar surface 460A and 460B, respectively, adapted toarticulate with the condylar surfaces of condyles 406 and 408. Agenerally planar surface 464 is oppositely disposed from the condylarsurface and is adapted to engage and connect to surface 440 of thetibial baseplate.

[0099] A ledge 468 extends around the outer perimeter and is adapted toengage shoulder 441 when tibial insert 420 and tibial baseplate 422 areconnected together. The tibial insert and baseplate can connect togetherin a variety of ways. Ledge 468 can snappingly engage into shoulder 441to firmly connect the tibial insert and baseplate. Further, these twocomponents can be adapted to connect permanently or removeably.

[0100] When the lateral component 450 and medial component 452 connecttogether, these two components form a complete, assembled tibial insert.In this assembled state, the tibial insert functions as a traditionalone-piece, integrally formed tibial insert. The assembled insert may beused as a bicompartmental tibial insert for total knee replacements.

[0101] As shown in FIG. 20E, once the lateral component 450 and medialcomponent 452 are connected, preferably they form a continuous andseamless junction or union where the condyles connect. No bumps, ridges,seams, indentations, channels, or the like should exist at the junctionwhere surfaces 406A and 406B meet (FIG. 20D). This may have variousconfigurations known to those skilled in the art to achieve a smoothpermanent or removeable connection. Such examples include, but are notlimited to, filling the transition with materials such as a biologichydrogel or designing and manufacturing to precise tolerances tominimize the effects of transition seams.

[0102] As shown in FIG. 20D, the prosthetic knee system 400 (includingthe femoral knee prosthesis 402, tibial insert 420, and tibial baseplate422) is divided across a single medial-lateral plane 480. This planessplits the prosthesis into two separate and distinct halves that aregenerally equal in size and shape on the medial and lateral sides.

[0103]FIGS. 21A and 21B illustrate a prosthetic knee system or acomplete knee prosthesis 500 adapted to be used for total kneearthroplasty. System 500 includes two main components, a femoral kneeprosthesis 502 and a tibial knee prosthesis 504. The femoral kneeprosthesis 502 comprises two separate and modular components, a lateralfemoral knee condyle 506 and a medial femoral knee condyle 508. Thesecomponents are identical to the condyles 302 and 304 discussed inconnection with FIGS. 19A and 19B, and reference should be made to thosefigures for a description of condyles 506 and 508. The tibial kneeprosthesis 504 includes two separate and modular components, a tibialinsert 520 and a tibial baseplate 522. These components are identical tothe tibial insert 420 and tibial baseplate 422 discussed in connectionwith FIGS. 20A-20E, and reference should be made to those figures for adescription of tibial insert 520 and tibial baseplate 522.

[0104] One skilled in the art will appreciate that many different meansexist for connecting the lateral and medial components of the tibialknee prosthesis of FIGS. 20 and 21. In this regard, the lockingmechanism could be configured as other types of tapered locking orpress-fit connections. The male and female components could be shaped ascylindrical projections and recesses, respectively. Further, the lockingmechanism could be configured to use a bayonet type connection orconfigured to snappingly engage each other. Further, the connectionbetween these two condyles can be permanent or removeable. Further yet,multiple locking mechanism can be employed. These mechanisms can bepositioned along the side surface or elsewhere on the femoral condyles.

[0105] One important advantage of the present invention is that all ofthe medial and lateral components in the prosthetic knee systems 400 and500 of FIGS. 20 and 21 are composed of modular components. All of theseindividual, separate components are adapted to be used in minimallyinvasive surgery (MIS) techniques. MIS is intended to allow for themaximum preservation of bone stock, restoration of kinematics, minimaldisturbance of the patellar tendon, and rapid rehabilitationpostoperatively. During an MIS knee surgery, a ½ to 3 inch incision ismade. The individual, separate components are small enough to fitthrough this incision. Thus, these components can be fit through theincision and then assembled in-vivo to form the prosthetic knee system.

[0106] During a traditional knee replacement surgery, the patella iseverted in order to place the femoral and tibial components. Oneimportant advantage of the present invention is that all of the medialand lateral components in the prosthetic knee systems 400 and 500 ofFIGS. 20 and 21 can be placed without everting the patella.Specifically, a small MIS incision is made on the lateral side of theknee, and a small MIS incision is made on the medial side of the knee.The lateral components are inserted through the lateral MIS incision,and the medial components are inserted through the medial MIS incision.The medial and lateral components are then assembled together in-vivo.Since the independent, separate components are small and assembledin-vivo, the natural patella of the patient is not required to beeverted.

[0107]FIGS. 20 and 21 show the tibial knee prosthesis having a medialand lateral tibial insert and a medial and lateral tibial baseplate.These components can be assembled in various ways to form the tibialknee prosthesis. As one example, the lateral tibial insert and lateraltibial baseplate can be separately positioned through the lateral MISincision. Once positioned in the lateral compartment of the knee, thesetwo components can be connected together to form the lateral portion ofthe tibial knee prosthesis. Next, the medial tibial insert and medialtibial baseplate can be separately positioned through the medial MISincision. Once positioned in the medial compartment of the knee, thesetwo components can be connected together to form the medial portion oftibial knee prosthesis. The lateral portion of the tibial kneeprosthesis and the medial portion of the tibial knee prosthesis can thenbe connected in-vivo to form the complete and assembled tibial kneeprosthesis.

[0108] As another example, some of the components of the tibial kneeprosthesis can be pre-assembled before inserting them through the MISincision. Specifically, the lateral tibial insert and lateral tibialbaseplate can be connected together outside of the patient to form thelateral portion of the tibial knee prosthesis. This lateral assembly canthen be positioned through the lateral MIS incision. Likewise, themedial tibial insert and medial tibial baseplate can be connectedtogether outside of the patient to form the medial portion of the tibialknee prosthesis. This medial assembly can then be positioned through themedial MIS incision. Once the medial and lateral assemblies are throughthe MIS incision, these assemblies can be connected to form the completeand assembled tibial knee prosthesis.

[0109] While preferred embodiments of this invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit or teaching of this invention. Theembodiments described herein are exemplary only and are not limiting.Many variations and modifications of the system, apparatus, and methodsare possible and are within the scope of the inventions claimed below.Accordingly, the scope of protection is not limited to the embodimentsdescribed herein, but is only limited by the claims that follow, thescope of which shall include all equivalents of the subject matter ofthe claims.

What is claimed is:
 1. A prosthetic knee system, comprising: a femoralknee prosthesis formed of two separate components, a lateral condyle anda medial condyle, wherein the lateral and medial condyles are assembledin-vivo; a tibial knee insert formed of two separate components, alateral insert adapted to articulate with the lateral condyle and amedial insert adapted to articulate with the medial condyle; and atibial baseplate formed of two separate components, a lateral baseplatecomponent and a medial baseplate component, wherein the lateral insertconnects to the lateral baseplate component, the medial insert connectsto the medial baseplate component, and the lateral baseplate componentconnects in-vivo to the medial baseplate component.
 2. The prostheticknee system of claim 1 wherein a femoral locking mechanism connects thelateral condyle to the medial condyle.
 3. The prosthetic knee system ofclaim 2 wherein a tibial locking mechanism connects the lateralbaseplate component to the medial baseplate component.
 4. The prostheticknee system of claim 3 wherein the tibial and femoral locking mechanismsinclude a male protrusion and a female recess.
 5. The prosthetic kneesystem of claim 4 wherein the tibial and femoral locking mechanisms forma Morse taper connection.
 6. The prosthetic knee system of claim 1wherein the lateral and medial inserts include a recess adapted toengage a shoulder on the lateral and medial baseplate components.
 7. Theprosthetic knee system of claim 6 wherein lateral insert is connectedin-vivo to the lateral baseplate component, and the medial insert isconnected in-vivo to the medial baseplate component.
 8. A modularprosthetic knee system, comprising: a femoral knee prosthesis formed oftwo separate and different components connectable together, a lateralcondyle and a medial condyle, wherein the lateral and medial condylesare connected together in-vivo; a tibial knee insert formed of twoseparate components, a lateral insert having an articulation surfaceadapted to articulate with the lateral condyle and a medial inserthaving an articulation surface adapted to articulate with the medialcondyle; and a tibial baseplate formed of two separate componentsconnectable together, a lateral baseplate component and a medialbaseplate component, the lateral insert being connected to the lateralbaseplate component, and the medial insert being connected to the medialbaseplate component, wherein the lateral and medial baseplate componentsare connected together in-vivo.
 9. The prosthetic knee system of claim 8wherein the lateral and medial condyles connect at a first junctionalong a medial-lateral plane.
 10. The prosthetic knee system of claim 9wherein the lateral and medial condyles connect at a second junctionalong an anterior-posterior plane.
 11. The prosthetic knee system ofclaim 10 wherein the first and second junctions form a seamlessinterface.
 12. The prosthetic knee system of claim 8 wherein the lateraland medial inserts connect at a junction along a medial-lateral plane.13. The prosthetic knee system of claim 12 wherein the junction forms aseamless interface.
 14. The prosthetic knee system of claim 8 whereinthe tibial knee insert and tibial baseplate are divided along amedial-lateral plane.
 15. The prosthetic knee system of claim 14 whereinthe lateral and medial inserts have a half-moon shape and connecttogether to form a substantially oval shape.
 16. A modular prostheticknee system implantable in a knee using minimally invasive surgery, theprosthetic knee system comprising: a femoral knee prosthesis formed of alateral condyle and a medial condyle, wherein the lateral and medialcondyles are separate components that are connected together in-vivo;and a tibial knee prosthesis having two separate components including alateral insert and baseplate and a medial insert and baseplate, thetibial knee prosthesis having an articulation surface for articulatingwith the lateral and medial condyles of the femoral knee prosthesis,wherein lateral insert and baseplate are inserted through a lateralincision in the knee and the medial insert and baseplate are insertedthrough a medial incision in the knee, the lateral insert and baseplatebeing connectable in-vivo to the medial insert and baseplate.
 17. Themodular prosthetic knee system of claim 16 wherein the tibial kneeprosthesis is divided along a medial-lateral plane to form the twoseparate components, the lateral insert and baseplate and the medialinsert and baseplate.
 18. The modular prosthetic knee system of claim 17wherein the femoral knee prosthesis is divided along the medial-lateralplane to form the two separate components, the lateral condyle and themedial condyle.
 19. The modular prosthetic knee system of claim of claim16 wherein the tibial knee prosthesis has a substantially oval shape.20. The modular prosthetic knee system of claim 19 wherein the lateralinsert and baseplate have a half-moon shape, and the medial insert andbaseplate have a half-moon shape.